Ketone bodies provide a supplementary or substitute form of energy that can be used during various metabolic states including stress, starvation, caloric regulation, or pathology. Oftentimes in diabetics, for example, low insulin levels and elevated blood glucose levels result in high concentrations of ketones in the body. This could potentially cause diabetic ketoacidosis (DKA).
The epidemic of diabetes in the United States will contribute to staggering medical costs, which can be limited by close ketone monitoring and maintenance. Patients in DKA experience many symptoms such as nausea, fatigue, and rapid breathing. They also emit a fruity odor in their breath, which is distinct and attributable to acetone. Acetone is a volatile ketone body released into alveolar air.
Untreated, DKA can result in coma or even death. However, DKA is preventable if ketone levels are monitored and treatment is sought when ketone counts are high. The current methods of ketone measurement are blood and urine analysis. The current blood tests typically are accurate, but their invasive nature is undesirable and frequently causes patients to delay treatment. Blood tests also are expensive, as a number of products are needed, including a lancet for blood letting, test strips, a specialized device and batteries. Several studies show that urine analysis is not accurate.
Ketone monitoring also is becoming recognized as a tool for nutritionists or health care professionals to monitor lipid metabolism during dieting. Several studies show that breath acetone concentrations represent lipid metabolism during a calorie deficit. Obesity has become increasingly prevalent and has now reached epidemic levels. It is consequently of great concern to healthcare professionals. Much effort has been invested in treating obesity and promoting healthy weight loss programs for obese individuals. For treatment of obesity, a sensor that measures fat burning is needed to adjust weight management plans to individual physiology. A non-invasive, inexpensive, simple-to-use acetone sensor would be an appropriate tool for nutritionists, physicians, and the general public who seek to monitor fat metabolism.
Some systems for measuring analytes in air operate on electrochemical principles (see, e.g., U.S. Pat. No. 5,571,395, issued Nov. 5, 1996, to Park et al.), and some operate by infrared detection (see, e.g., U.S. Pat. No. 4,391,777 issued Jul. 5, 1983, to Hutson). U.S. Pat. No. 6,658,915, issued Dec. 9, 2003, to Sunshine et al., describes using chemically sensitive resistors to detect airborne substances and requires the use of an electrical source.
U.S. Pat. No. 4,935,345, issued Jun. 19, 1990 to Guilbeau et al., describes the use of a single thermopile in liquid phase chemical analysis. However, the thermopile sensor is limited to measuring a single analyte and only a single reactant is present on the thermopile. This sensor operates in the liquid phase. Each of the foregoing patents is hereby incorporated herein by reference as if fully set forth herein.
A fast, inexpensive, non-invasive method of measuring analytes in fluids, particularly gas, is needed.